What you will need

• A working Duckiebot: Duckiebot Subsystems

• A functional dts installation: Duckietown Shell (dts)

• A camera calibration pattern, such as one provided in a Duckiebox.

What you will get

• A Duckiebot whose extrinsics camera calibration has been completed.

Intrinsic camera calibration

The intrinsic camera calibration procedure identifies parameters that define the relationship between the 2D image plane and the 3D world around the Duckiebot. These parameters account for various optical specifications such as the camera’s focal length, the pixel aspect ratio, and the distortion field applied by the fisheye lens.

Tip

For optimal performance, repeat this procedure if you change the focus of the camera by rotating the lens.

The Intrinsics Calibrator

Attention

Before proceeding, make sure that you can ping your Duckiebot using the following command, where DUCKIEBOT_NAME is the name of your Duckiebot:

ping DUCKIEBOT_NAME.local

Ubuntu

To open the Intrinsics Calibrator, run the following command, where the --browser flag opens the WebGL (browser) version:

dts duckiebot calibrate_intrinsics DUCKIEBOT_NAME [--browser]

Duckietown Workspace

To open the Intrinsics Calibrator, if dts is installed on the host machine, run the following command from a terminal inside the Duckietown Workspace or on the host machine:

dts duckiebot calibrate_intrinsics DUCKIEBOT_NAME

Note

This command will be delegated to the host machine if it is run inside the Duckietown Workspace.

Note

The first time a Duckietown Viewer app is run, a pop-up window may appear and request permission. Enter your password and select “(Always) Allow” to continue.

Alternatively, to open the WebGL (browser) version of the Intrinsics Calibrator, open a terminal inside the Duckietown Workspace or on the host machine (if dts is installed on the host machine) and run:

dts duckiebot calibrate_intrinsics DUCKIEBOT_NAME --browser

Fig. 64 The Duckietown intrinsics camera calibration interface.

Note the keys in the table below.

Key	Function
X	Increase the Frame Rate
Z	Decrease the Frame Rate
Space	Calibrate the camera
F	Toggle the Undistort switch
R	Refresh the window
T	Open the Debug Console

Intrinsic calibration procedure

To perform the intrinsic calibration procedure:

1. Move the calibration pattern in front of your Duckiebot’s camera such that the entire checkerboard pattern is within its field of view and colored lines begin to overlay the checkerboard pattern.

2. Rotate the mechanical focus ring on the lens until you can clearly read the x and y labels on the checkerboard pattern (do not adjust the focus again or place the lens cover back onto the lens unless you plan on repeating this procedure).

3. Slowly move the calibration board left, right, up, down, forwards and backwards, relative to your Duckiebot’s camera, until each region within the x, y and Size bars is filled in.

4. Slowly tilt and pan the calibration board, relative to your Duckiebot’s camera, until each region within the Skew bar is filled in.

5. Click the Calibrate button.

6. Wait for the spinner to disappear.

7. (Optional) Click the Undistort switch to see an undistorted view of what your Duckiebot sees.

Fig. 65 The Duckietown intrinsics camera calibration interface (Intrinsics Calibrator) with all of its bars filled in.

Fig. 66 The Intrinsics Calibrator with the Undistort switch set to on.

To confirm that a new intrinsic calibration file has been created on your Duckiebot, run the following command and inspect the contents of the Camera Intrinsic panel:

dts duckiebot dashboard DUCKIEBOT_NAME --page robot/calibrations

Fig. 67 The Camera Intrinsic panel on the Robot page of the Dashboard.

Note

Within the Camera Intrinsic panel, under Local, you should see a tick next to Completed, the calibration date next to Calibration date and /data/config/calibrations/camera_intrinsic/DUCKIEBOT_NAME.yaml next to Files.

Troubleshooting

Troubleshooting

SYMPTOM

When I open a calibrator window, I see a gray loading screen instead of images in the center. I know that the camera otherwise works on my Duckiebot.

RESOLUTION

Press the refresh icon on the top right of the calibrator window to restart the image stream.